Process of frosting glass



Patented Mar. 31, 1942 raoonss F FROSTING GLASS Daniel P. Gallagher, Harrison, N. J.

' No Drawing.

This invention relates to a new and improved process of frosting glass of general application,

but particularly applicableto the inside frostin of glass bulbs suchas the bulbs used for making incandescent lamps.

It'is an object of this invention to provide a new and improved method of frosting which will give a surface having high light diffusion propertiesjwith a minimum of light absorption and which- "will be relatively smooth and easily cleaned.

Since the invention is particularly applicable to lamp'bulbs I have chosen that application for illustration. I

It has heretofore been proposed to impart in-' side ,frosting to electric lamp bulbs'by various solutions involving hydrofluoric acid and ammonium fluoride, but-such processes have involved a distinct disadvantage'in that as ordinarily adapted they have produced, as a result of the frosting operation, abulb which was too fragile for commercial handling orfor manufacture into anincandescent lamp.

It has been proposed to remedy this situation by a second treatment of the bulbs with weakened solutions of the same composition or substantially the same composition which reduces the fragility of the bulb without materially affecting the frosting. Such a compound process, however, is not only expensive in its operations because it requires two or more separate and distinct steps but-it also produces a frosting of coarse texture which absorbs a materialquantity of light. It also produces a bulb having great variations in the surface so that if it becomes soiled in any manner it is quite difficult, if not,impossible,

thoroughly to clean.

It is an object of this invention to provide a new and improved process of frosting bulbs which, in a single operation, will produce a frosted bulb free from any need of fortification having direct from the frosting solution its full strength and requiring no second-operation.

It is a further object to provide a new and simple process by which a superior frosting can be obtained giving an effective light diffusion with a minimum of light absorption and which, moreover,'wi1l have a relatively smooth surface that can, if necessary, be readily cleane'd.

It is a further object to provide a method of frosting bulbs which can be operated at normal factory temperatures.

In accordance with this invention it has been discovered that if therebe added to a frosting solution a material percentage of commercial deto retain the dirt.

tially composed of 100 parts of ethyl alcohol and.

Application November 22, 1938, Serial No. 241,826

6 Claims. (c1.

natured alcohol that the operation of the solution upon the glass is materially altered. The etching produced by this new process is free fromperceptiblesharp edges or sharp indentations and produces a translucent effect in place of the whitish effect heretofore in use and this translucent effect createsahigh degree of dispersion of the'lightat the same time it produces a high' tr ansmission. This new type of surface when used uponthe exterior of the bulb possesses the distinct advantage that the surface may be easily washed as there are no deep sharp cracks The invention has special merit, however, in the" inside frosting of the bulb because the bulb direct from the etching solution is free from strains and is of full strength without any so-called fortification. The composition which I have found effective for this purpose is as follows':

t, v Per cent Hydrofluoric acid 23 Ammonium bifluoride 20 Sodium bicarbonate -4--. 4 Denatured alcohol e 33 Sodas--- 10 Water 10' The denatured alcohol employed-is substan- 5 parts methyl alcohol and 5 parts of a solution containing 5 parts of ethyl acetate in one' The percentagev of these components may be varied within considerable limits but the result achieved is apparently'due to the presence of these elements in combination, for I have not found that the use of these individual elements taken separately produces satisfactory results.

The frosting solution may be applied to the glass at any temperature but it operates satisiactory at room temperatures. It may remain in contact with the glass for a predetermined time, dependent upon the extent to which the frosting is to be carried, and thereupon the solution may be removed and the glass washed without the necessity of other steps.

The process above described produces, in one operation, results which are superior to those which have heretofore been produced with two or more operations and the fact that it may be conducted at room temperatures makes it possible to eliminate the need for steam or heating equipmen Since certain changes incarrying out the above "process may be made without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, 'what I claim as new and desire to secure by Letters Patent, is:

l. The process of imparting an inside frost to a glass bulb which comprises subjecting the bulb to a solution comprising substantially 23% hydrofluoric acid, 20% ammonium bifluoride, 4% sodium bicarbonate, 33% denatured alcohol, 10% soda and 10% water.

2. A process in accordance with claim 1 in which the denatured alcohol comprises 100 parts of a solution made up oi 100 parts of ethyl alcohol and 5 parts of wood alcohol to which is added ,5 parts of a solution made up'of 5 parts of ethyl acetate and one part of aviation gas.

4. The process of inside frosting a bulb which comprises subjecting it to an etching solution taining fluorine as its active ingredient and having a suflicient addition of denatured alcohol to the etching solution to prevent weakening of the bulb during normal etching and washing the same without fortification, the percentage of alcohol being between 20% and 55%.

6. The process of inside frosting a bulb for an Y incandescent lamp which comprises subjecting 3 The process of imparting an inside frost to 2b a glass bulb which comprises subjecting the bulb to an etching solution containing substantially 33% denatured alcohol.

it to an etching solution containing a disassociable compound of fluorine and sumcient. quantity of denatured alcohol to prevent weakening the bulb during a normal etching, the percentage of alcohol being between 20% and 55%.

DANIEL P. GALLAGHER. 

